Colorramp node makes colors clip or blow out
Color Ramp, nor any thing in Blender, is pixel managed.

As a result, I believe the Color Ramp is taking the scene referred 0.0 to 1.0 range and clipping it, which is leading to the harsh cut transition from 1.0 scene referred onwards.

The complex solution is to mangle the data going to and from the Color Ramp. The more elegant and powerful solution is to pixel manage every single UI element to permit the audience to control the context of the tool to meet the need.